A road surface reflection detecting apparatus has been proposed as an apparatus for determining whether the surface of a road is shiny. An example of the road surface reflection detecting apparatus is disclosed in JP 2000-180378A.
In accordance with this road surface reflection detecting apparatus, light beams generated by a light source are radiated to a location on the surface of a road and the picture (image) of the radiated location is taken. Then, a portion of the picture included in a predetermined cutout range with luminance at least equal to a predetermined threshold value is extracted as a partial picture based on regularly reflected light beams. Finally, the area and aspect ratio of the partial picture are compared with reference value to determine whether the surface of the road is shiny.
In addition, in a configuration including a camera mounted on the vehicle for taking a picture, a light beam reflected from a reflection plate provided on a road side to which an illuminant on the vehicle radiates a light beam is used for determining whether the surface of a road is shiny.
The conventional road surface reflection detecting apparatus extracts a picture with high luminance based on a picture in a predetermined cutout range. In a configuration including a camera mounted on the vehicle for taking a picture, however, a road in front of the vehicle can be a straight or curved road. Thus, with the predetermined cutout range, a picture on a road surface cannot be cut out properly from a taken picture.
When a cutout range is predetermined based on a travel motion condition on a straight line, for example, in a travel motion condition of a curved line, a road-side body (obstacle) such as a guard rail appears on the picture in the cutout range in some cases. In such cases, for example, the headlight beam of the vehicle is reflected by the guard rail, forming an area with high luminance. Thus, the light beam reflected by the guard rail is detected erroneously as a shiny state of the road surface.